The FDA gave the green light to Arena Pharmaceuticals to sell Belviq, or lorcaserin generically, a twice-a-day pill that suppresses appetite and appears to affect metabolism by influencing levels of the brain chemical serotonin.

"Obesity threatens the overall well-being of patients and is a major public health concern," Janet Woodcock, director of the FDA's drug center, said in a statement. "The approval of this drug, used responsibly in combination with a healthy diet and lifestyle, provides a treatment option for Americans who are obese or are overweight and have at least one weight-related comorbid condition."

The drug was approved for obese people (those with a body mass index of 30 or more) and overweight people with a BMI of 27 or more who also have at least one weight-related health condition, such as high blood pressure, Type 2 diabetes or high cholesterol.

In studies sponsored by Arena, about half of patients taking Belviq lost about 5 percent of their body weight after a year. The most common side effects include headache, dizziness, fatigue, nausea, dry mouth, and constipation.

The FDA had rejected the drug in 2010 after a panel of experts advised the agency to give it a thumbs down because of safety concerns. Early studies indicated the drug might cause tumors in rats and possibly heart problems in people. Lorcaserin works the same way as one part of the fen-phen diet pill combination that was pulled from the market in 1997 because it caused heart valve damage.

But the company submitted new data aimed at alleviating those concerns, and the same panel endorsed approval in May. Some panel members, however, again expressed concerns about the drug's safety, especially the heart problems, as have some consumer advocates.

"Faced with this serious concern, it would be dangerous and unconscionable for you to allow the FDA to disregard the available evidence and subject large numbers of obese patients, already at risk for cardiovascular disease, to the added risk of damaged heart valves," wrote Sidney M. Wolfe of the Public Citizen Health Research Group, in a letter to FDA Commissioner Margaret A. Hamburg.

Arena will be required to conduct six additional studies to monitor the drug's safety, including one specifically designed to examine cardiovascular risks, the FDA said.

The company told Shots it doesn't yet know the price for Belviq or when it will be available in pharmacies.

Late Wednesday, Arena CEO Jack Lief said on CNBC that Belviq would cost about the same as a Starbucks venti latte in New York. TheStreet.com reported the drug is expected to be available in pharmacies in four to six months.

The agency has been under pressure to make it easier for weight-loss drugs to get to market. More than two-thirds of Americans are overweight, including about one-third who are obese.

Despite millions of dollars in research, only a handful of government-approved weight-loss drugs are on the market, and only one, Orlistat, can be used long-term. The FDA hasn't approved a new weight-loss drug since Orlistat came on the market in 1999. Although it's now available without a prescription under the name Xenical, that drug isn't all that effective and can cause unpleasant side effects, most notably diarrhea.

The once-popular weight-loss drug Meridia was pulled from the market in 2010 because of concerns about heart attacks and strokes.

In February, FDA advisers also recommended approval of Qnexa, another weight-loss drug. The FDA had rejected Qnexa in 2010 because of concerns about heart problems and birth defects.

But Vivus, maker of Qnexa, submitted additional data aimed at alleviating those concerns. In April, the FDA said it was delaying a final decision on Qnexa until July 17. Qnexa is a combination of two drugs that are already on the market: phentermine, a stimulant used for short periods to help control weight, and topiramate, which is used for migraines and seizures.

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Transcript

LINDA WERTHEIMER, HOST:

This is MORNING EDITION, from NPR News. I'm Linda Wertheimer.

RENEE MONTAGNE, HOST:

And I'm Renee Montagne. The Food and Drug Administration has approved the first new weight-loss drug in 13 years. That decision comes after a series of disappointments in the hunt for new ways to help seriously overweight people lose that weight. NPR's Rob Stein reports.

ROB STEIN, BYLINE: The new drug is called Belviq. It works by triggering a switch in the brain that ends up suppressing appetite. Abraham Thomas. at the Henry Ford Hospital in Detroit, led a panel of experts that reviewed the drug's safety and effectiveness for the FDA.

DR, ABRAHAM THOMAS: On average, in most patients, it caused about 5 to 8 percent of weight loss. Some patients lost more than 10 percent.

STEIN: Based on that, the FDA approved Belviq for two types of patients - people who are obese, meaning they have a body mass index of at least 30; and people who are just very overweight but also have at least one health problem, like high blood pressure, high cholesterol or Type 2 diabetes. James Zervios is with the Obesity Action Coalition, which has been pushing for new weight-loss drugs.

JAMES ZERVIOS: There's 72 million adults affected by obesity. Now, they have something to look at, to combat this disease.

STEIN: With the obesity epidemic raging out of control, there haven't been many options. The last weight-loss drug the FDA approved, in 1999, doesn't work very well, and it has side effects. Diets and exercise only help a little. Surgery works, but it's pretty much a last-ditch option. Scott Kahan is at the George Washington University.

DR. SCOTT KAHAN: Of course, healthy eating and physical activity, is an important strategy. But on its own, that's not enough. We've been trying that for decades, and obesity rates have only increased.

STEIN: But not everyone is pleased by the FDA's decision. The big worry is safety. The FDA had rejected Belviq once before, because of safety concerns. The main worry is that it might damage people's hearts. Sidney Wolfe is with the Public Citizen Health Research Group, a consumer advocacy group.

DR. SIDNEY WOLFE: Some doctors who are treating people who are overweight - and unfortunately, the FDA - are so desperate that they seem to be throwing caution to the winds.

STEIN: Wolfe pointed out that earlier weight loss drugs, like fen-pfen and Meridia, were both pulled off the market for causing heart problems. And Belviq is similar to fen-pfen in some ways.

WOLFE: The history of diet drugs in this country is a grim history; of one after another coming on the market, and then having to be taken off the market after the damage that they cause was suspected.

STEIN: But the FDA concluded that the benefits of the drug outweighed the risks, which so far seem generally minor. Proponents argue that the FDA's decision marks an important shift when it comes to weight-loss drugs. They're not just diet pills that people take for cosmetic reasons. They're needed to treat a serious disease. So like drugs for heart disease and cancer, some risks might be acceptable. James Zervios again, with the Obesity Action Coalition.

ZERVIOS: This is a serious epidemic, and we have to do something about it. And I think that message is finally beginning to penetrate. This is about health. This is not a cosmetic issue.

STEIN: Abraham Thomas, who headed the FDA panel, agrees.

THOMAS: There's no medication that is 100 percent safe. And what we're trying to do is balance the risks of the medication versus the benefits of treating obesity.

STEIN: The FDA is requiring the company that makes Belviq to conduct six additional studies, to see if the benefits for treating obesity do, indeed, outweigh any risks.